Microprocessors are finding increasing applications as intelligent control devices in the home as well as in industry. When a plurality of such microprocessors are interconnected by means of a common data bus, various protocols are used for orderly information transfer, such as described within U.S. patent application Ser. No. 561,483 filed 12-14-83 of E. K. Howell et al, which application is incorporated herein for purposes of reference.
When the common data bus includes a broadband communication bus, such as a power line communication bus which contains a modulated high frequency carrier signal along with the power frequency, transceivers are used which must be capable of converting the modulated carrier to baseband data for utilization by the microprocessor as well as converting the baseband data from the microprocessor to modulated carrier for transmission on the power line communication bus. State of the art transceiver devices require four terminals for interconnection with a microprocessor to provide input data, output data and control of the transmitter and receiver sections of the transceiver, and hence are not suitable for direct connection to a two-conductor baseband data bus. Such transceiver devices also exhibit a low impedance to the broadband terminals in both receive and transmit modes of operation, hence causing attenuation of the carrier signals when a plurality of transceivers are connected to a two-conductor broadband data bus.
A carrier current digital data transceiver requiring only two terminals for interconnection with a microprocessor or a baseband data bus is described within the aforementioned Howell et al application. The Howell et al transceiver is designed using discrete components which, although achieving excellent results in industrial applications, do not readily lend to miniaturization, such as when required to be used with home appliances connected to the power bus by wall outlets.
The carrier current digital data transceiver of the instant invention provides transparent interface function between broadband data and baseband data buses along with sufficient logic and impedance control to overcome all the aforementioned problems involved with several microprocessors along a common data bus. The selection of circuit elements and functions allows the transceiver to be fabricated within an integrated circuit in a compact and efficient configuration.